// run: $exec < input
#include <iostream>
#include <algorithm>
#include <vector>

std::vector<int> v;
int n;

int main()
{
	std::ios::sync_with_stdio(false);
	std::cin >> n;
	v.resize(n);
	for (int i = 0; i < n; i++) std::cin >> v[i];
	std::sort(v.begin(), v.end());
	auto last = std::unique(v.begin(), v.end());
	v.erase(last, v.end());
	n = v.size();
	bool opt = false;
	for (int i = 0; i + 2 < n; i++) {
		if (v[i + 2] - v[i] <= 2) {
			opt = true;
			break;
		}
	}
	std::cout << (opt ? "YES" : "NO") << '\n';
}

